WO1994001635A1

WO1994001635A1 - Composite-action roof truss system

Info

Publication number: WO1994001635A1
Application number: PCT/US1993/006427
Authority: WO
Inventors: John D. Breitenbach
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-07-10
Filing date: 1993-07-08
Publication date: 1994-01-20
Anticipated expiration: 1995-01-10
Also published as: AU4668493A

Abstract

A standing seam roof truss system (20) providing for composite action includes a V-truss (24), a pair of elongated beams (26, 28) connected at the upper ends of the V-truss, a deck member (30) in spanning relationship to the V-truss, and struts (58) which reinforce the V-truss across the top thereof and connect the V-truss system to an adjacent V-truss system. The deck members (30) are constructed as a sandwich panel and include a shoulder (144) at each side which is supported by and preferably conforms to the surface of the beams for transmitting forces thereto, the deck member being mechanically locked to the beams, preferably by screws (148). The standing seam deck members are easy to assemble and thus act together with the beams as compression members to carry vertical and horizontal loads.

Description

COMPOSITE-ACTION ROOF TRUSS SYSTEM

Background of the Invention

1. Field of the Invention

This invention cc ^erns a V-shaped roof truss system which includes the roof deck as an integral structural element of the design. The roof truss system hereof is nestable in storage and transit, employs a standing seam with no exposed fasteners, and provides a composite beam action which provides an efficient truss design with a minimum of vertical deflection as well as transmitting loads in directions both substantially normal to and transversely across said deck.

2. Description of the Prior Art

Prior methods of structural support of roof decking have usually been comprised of roof purlin systems using cold-rolled C or Z shapes, bar joists, wide flange beams and the like, all using steel materials. Wood materials are also used for purlin and joist systems. Alternatively, a number of V-truss systems have been developed for use in supporting roof decking. These systems include those shown in U.S. Patent No. 3,091 ,313 to Colbath, U.S. Patent No. 4,349,996 to Lautensleger et al., and U.S. Patent No. 4,435,932 to Seaburg, et al.

Structures as disclosed in these references have been designed to transfer a horizontal wind shear or force; however, these systems do not use the roof deck as a compression element in the beam action design and thus do not demonstrate composite beam action. Composite beam action may be understood as including any mechanically attached top membrane as an integral compression element or member in the design or vertical load carrying capability of the entire structural unit, in this case the V-truss & deck unit. In the case of roof systems, the roof deck or membrane functions as an integral top chord. Conventional roof deck systems have been constructed which are securely welded or fastened to the underlying supporting member, and which transfer horizontal forces. However, these systems are not designed for composite action.

There has thus developed a need for a roof system which includes a lightweight upper deck and provides for composite beam action which will result in the most efficient V-truss member design with the least amount of vertical deflection. A need has also developed for a V-truss which: is stackable for manufacture and shipment; is stable and safe during and after roof erection; provides for an integral system of the joist and roof deck which will transmit horizontal wind and seismic forces; which will combine and use the benefits of a standing seam roof system with composite design and horizontal diaphragm force action; will enable the assembly and lock-down for partial or full composite action of the top truss panel and positioning of secondary panels on the V-truss for hoisting to the roof, all to be performed on the ground; will provide a press formed connection design that will not only facilitate stacking of the V-trusses, but will allow for factory assembly and welding of the open "V"; will provide a total assembly capable of withstanding required uplift loads per current building codes; and will provide a lighter weight structural system with less deflection than conventional bar joists and other V-trusses for the same load-carrying capacity.

Summary of the Invention

These objectives are met by the composite action V-truss system of the present invention, which employs a standing seam and presents a high strength-to-weight ratio. The roof truss system of the present invention utilizes the roof deck as the top chord of the truss to act as a load bearing member both for vertical loads and for horizontal or diaphragm loads including seismic and wind shear.

The roof truss system hereof includes a pair of elongated beam chords as part of a V-truss, the diagonals and bottom chord portions of the V-truss; a roof deck in the form of a panel having an upper membrane and a lower membrane, and means for connecting the deck to the beams whereby the deck supports loads placed thereon and transfers horizontal loads therealong so that adjacent decks transfer forces therealong. The decks present upstanding flanges of a standing seam design for efficient installation and the truss system is constructed so that much of the assembly can be completed before hoisting into roof position. Preferably, the system hereof includes a removable cross strut whereby a number of such trusses can be stacked for storage or transportation and then ground assembled prior to hoisting on the site to be carried by conventional girders, concrete or masonry walls, other trusses or structures well-known to those skilled in the art and not forming a part of the claimed invention.

In preferred embodiments, the deck is provided in a plurality of layers having insulation, such as foam insulation, sandwiched between the upper membrane and the lower membrane. Each side of the deck member presents a standing seam and a shoulder positioned therebelow which is mounted to the beams. The shoulders are configured to engage the beams and thereby transmit force directly thereto. Preferably, holes are selectively provided in a longitudinally extending lip to receive screws therethrough for attaching the deck to the beam. The deck is preferably provided with stiffening indentations extending transversely to promote the transfer of horizontal or diaphragm loads, as well as downward and uplift loads. A reinforcing strut may be so designed and positioned in vertically spaced relationship below the lower membrane of the deck to provide additional support under extreme loading conditions.

The V-truss also preferably includes, in addition to V-struts lying in a substantially vertical plane and positioned at intervals along the strut, a plurality of secondary struts which are inclined in a longitudinal direction to provide longitudinal stability as well as vertical support. The V- struts and the secondary struts are both connected to the bottom chord of the strut and to a connecting plate. The connecting plate is most preferably press-formed to provide recesses for respectively receiving one leg of each the V-struts and the diagonal secondary struts, thereby allowing all members to be accurately positioned and easily welded at the centroidal position of the respective legs and plates providing greater fabrication and cutting error tolerance in manufacturing. Additionally, the plates are interconnected longitudinally by a stabilizer rod to secure integrity during handling. Each plate includes a stiffener indentation for improving the stiffness of the plate, as well as holes for receiving both the transversely extending stabilizer struts across the V-truss and the connecting struts which transversely connect one V-truss to an adjacent V-truss in the system. While the connecting plates, stabilizer rods, V-struts and secondary struts are preferably welded in place, the stabilizer struts and the connecting struts are mounted by threaded fasteners whereby the V- truss can be stacked until ready for use, and then later connected to the beams. All stabilizer struts and connecting struts are installed at the time of field erection.

Under downward dead and live loads, the deck and the V- struts and secondary struts are in simultaneous compression and tension respectively as a unit, and under uplift loads the deck, V-struts and diagonal secondary struts may alternate stresses, depending on the roof loading. The shoulders of the deck members are configured to, together with the fasteners connecting the deck to the beams, transfer vertical loads into composite action with the V-truss and transfer horizontal or diaphragm forces across the deck membrane.

These and other features of the invention will be apparent in view of the drawings and the description of the preferred embodiment.

Brief Description of the Drawings

Figure 1 is a top front perspective sectional view of a V-truss system used in connection with the roof deck and connecting struts to comprise the composite action roof truss system of the present invention;

Fig. 2 is a top plan view of one section of the V-truss system hereof without the deck member;

Fig. 3 is a vertical cross sectional view of the V-truss system hereof through line 3-3 of Fig. 2;

Fig. 4 is an enlarged, vertical cross sectional view of the composite action roof truss system hereof showing the roof deck, the reinforcing strut and the connecting strut for connecting adjacent V-truss members;

Fig. 5 is an enlarged fragmentary perspective view of the connecting plate showing portions of the respective reinforcing strut, connecting strut, V-strut, secondary strut and stabilizer rod in their respective positions;

Fig. 6 is an enlarged, fragmentary view of the composite action roof truss system hereof showing the standing seam connection of adjacent deck members with their insulation shown in section, and showing the deck members mounted to a C-beam; Fig. 7 is an enlarged, fragmentary view of the composite action roof truss system hereof similar to Fig. 6 but showing the deck and V-truss connected to an angle beam;

Fig. 8 is an enlarged, fragmentary left side elevation view of the V-truss hereof showing the V-strut and the secondary strut welded to the bottom chord and secondary chord positioned thereabove;

Fig. 9 is an enlarged exploded view in perspective, showing portions of two adjacent deck members in position for mounting to a beam, with portions of the standing seam wall of one of the deck members broken away for clarity;

Fig. 10 is an enlarged, fragmentary front elevational view of the connecting strut and the reinforcing strut mounting to the connecting plate, with the bottom membrane of the deck member shown spaced above the reinforcing strut; and

Fig. 11 is an enlarged, fragmentary top plan view showing the connecting strut and reinforcing strut mounted to the connecting plate.

Description of the Preferred Embodiment

Referring now to the drawing, a composite action roof truss system 20 broadly includes a V-truss system 22 including a V-truss 24 and a pair of opposed, longitudinally extending, parallel, elongated beams 26 and 28, a deck member 30, and a connecting strut 32 as seen in Fig. 1 and Fig. 4. The V-truss system may be connected in series to additional V-truss systems and ultimately is supported in a conventional manner at the longitudinal ends thereof by girders, concrete or masonry walls, or the like. In the composite roof truss system 20 hereof, a plurality of V-truss systems 22A and 22C may be employed for supporting deck members 30A and 30C positioned thereabove, as well as deck member 30B supported in spanning relationship between adjacent V-truss systems as shown in Fig. 4.

In greater detail, V-truss 24 includes a longitudinally extending bottom chord 34, bottom chord secondary rods 36 and 38 welded thereabove, a plurality of primary V-struts 40 each presenting legs 42 and 44, a plurality of stabilizer struts 46 each presenting longitudinally inclined arms 48 and 50, connecting plate 52, longitudinally extending stabilizer rods 54 and 56, and removably mounted reinforcing strut 58. The V-struts 40 and stabilizer struts 46 are welded to bottom chord 34 at welds 60 and 62 respectively as shown in Fig. 8, and each connecting plate 52 is welded to a respective leg of V-strut 40, an arm of a stabilizer strut 46, and a stabilizer rod 54. Thus, these components are welded together as a unit and not separable, whereas reinforcing strut 58 may be connected to the connecting plate 52 by a threaded fastener.

Primary V-strut 40 is preferably, though not necessarily, a unitary length of steel rod or tubing which is bent into a V-shape to thereby present a pair of divergent legs 42 and 44. V-strut 40 lies in a plane which is substantially perpendicular to bottom chord 34, this being normally vertical in practice. Stabilizer struts 46 are also preferably, though not necessarily, formed of a unitary length of steel rod or tubing and are also bent into a V shape. However, stabilizer struts 46 lie in a plane which is skewed relative to the bottom chord 34 and are inclined longitudinally whereby the apex 64 of stabilizer strut 46 is adjacent the apex 66 of a respective V-strut but the remote end 68 of stabilizer strut 46 is welded to the next longitudinally successive connecting plate 52 relative to the remote end 70 of the respective V-strut 40. Stabilizer struts 46 thus provide vertical load carrying capacity as well as support in a longitudinal direction against horizontal or diaphragm stresses. Bottom chord 34 extends longitudinally and is constructed of steel rod or tubing, while bottom chord secondary rods 36 and 38 welded thereto forming a compound bottom chord are also of steel but need not extend the full length of the bottom chord 34 but rather provides support where the greatest bending moment can be expected along the longitudinal midsection thereof.

Connecting plate 52 is preferably formed in a press for economy but could alternatively be forged. Each connecting plate 52 includes a normally upright wall 72 and a normally transversely inclined flange 74 angled downwardly and inwardly along bend 76 toward apex 66. A stiffener indentation 78 is formed in the plate 52 presenting a ridge 80 oriented transversely to bend 76 to provide resistance to the tendency of plate 52 to excessive bending and maintain the relative angle between wall 72 and flange 74. Wall 72 also includes a pair of longitudinally spaced holes 82 and 84 for respectively receiving fasteners associated with connecting strut 32 and reinforcing strut 58. Flange 74 presents a leg recess 86 and an arm recess 88 for respectively receiving leg 42 (or leg 44) and arm 48 (or arm 50) therein. The recesses 86 and 88 serve to locate the respective remote end of each leg and arm and not only provide a greater surface area than a flat surface for welding, but also keep the leg and arm approximately centered on the flange 74 with respect to their diameters. That is to say, the centroid or diametrical center line of each the arm 48 and leg 42 will be aligned with the substantially flat plate 52 because the respective recesses 88 and 86 conform to the arcuate outer surface of the respective arm and leg.

Reinforcing struts 58 provide lateral stability to beams 26 and 28 and may be formed of an elongated solid rod, of tubular material, or of an angle bar as shown in Fig 5. Reinforcing strut 58 presents a pair of ends 90 and 92 and is oriented in a transverse direction and preferably perpendicular relative to bottom chord 34. Adjacent each end 90 and 92, a pin 94 is affixed by welding or the like, the pin having a threaded portion for receiving a nut 96 thereon. The pin is positioned to extend from the respective end 90 or 92, thereby enabling the threaded portion of the pin 94 to extend through the connecting plate 52 and the respective beam 26 or 28 and secured in position by threading nut 62 thereon. In this manner, the reinforcing strut is removably mounted so that multiple V-trusses 24 may be stored in a stack 98 supported or separated by blocks 100 of, e.g., wood as shown in Fig. 12. Only a single reinforcing strut 58 is mounted on the bottommost V-truss 24 for stabilization.

Connecting strut 32 may also be constructed of elongated solid steel rod, tubing or angle iron as shown in Fig. 5. Each connecting strut 32 presents a pair of opposed ends 102 and 104 having a mounting plate 106 welded thereto, the mounting plate 106 having an aperture 108 therethrough for receiving a bolt 108. The bolt 108 threadably carries a nut 110 for securing the connecting strut 32 to a respective beam and its associated connecting plate 52. The connecting struts 32 typically extend between the connecting plates 52 of adjacent V-trusses 24 to provide resistance to horizontal stresses in a direction transverse to the longitudinal axis of the V-truss 24. Beams 26 and 28 function as the top chords of the V-truss system 24 and may be of varying configurations, such as a cold formed steel C channel shown as beam 26A in Fig. 6, or alternatively a hot roll steel angle shown as beam 26B in Fig. 7. The beams 26 and 28 are preferably formed of 14 through 10 gauge steel, but may be of different thicknesses and alloys as conditions and design loading dictate. Beam 26A is elongated and presents a central bight 112 and a pair of feet 114 and 116 extending normally horizontally therefrom, each terminating in a rim 118. Beam 26B is also elongated and presents a normally upright back 120 and a normally horizontal head 122 at the upper end thereof. The head 122 of beam 26B and the foot 116 of beam 26A provide surfaces for receiving the deck member 30 thereon.

Deck member 30 presents an upper membrane 124 and a lower membrane 126 having an insulation layer 128 sandwiched therebetween. The upper membrane 124 is preferably of galvanized and colored sheet metal of sufficient thickness to provide a load carrying capacity such as 22 or 24 gauge. The upper membrane 124 presents a substantially flat stretch 130, extends upwardly to present a standing seam flange 132 with lip 134, and then downwardly to lap 136. The insulation layer 128 is preferably a synthetic resin foam such as polyurethane exhibiting good adhesive properties to hold upper membrane 124, lower membrane 126 and insulation layer 128 together as a unit with sufficient structural rigidity to act as a load carrying member. Each lap 136 provides a surface for mounting the deck member 30 to a respective beam 26.

Lower membrane 126 presents a base 138 which includes a plurality of longitudinally spaced corrugations 140 which extend transversely across the base 138 to provide enhanced rigidity. Base 138 curves upwardly to present a shoulder 144 including riser 142 which continues to a bend 143 extending to lap 136, the shoulder 144 serving to support the deck member 30 on the respective beam 26 or 28. Riser 142 of shoulder 144 engages the rim 118 of beam 26A to provide additional horizontal load transferring ability in a generally transverse direction.

Shoulder 144 extends to lap 136, and both the upper membrane and the lower membrane in the vicinity of lap 136 are provided with holes to receive therethrough the shanks 146 of sheet metal screws 148 which penetrate into the respective beam and fasten the deck member 30 thereto. As shown in Fig. 9, the lap 136 at one side 150 of each deck member 30 is provided with holes 152 of sufficient diameter to permit only the shanks 146 of the screws 148 to pass therethrough with the heads 154 of the screws holding the lap 136 down. However, at the other side 156 of the deck member 30, holes 152 alternate with openings 158 which are large enough to permit the heads 154 to pass therethrough. As shown in Fig 9, the screw 148 passing through opening 158 will directly engage the lap 136 of the first side 150 of deck member 30 without interference from the lap 136 surrounding the opening 158 of the other side 156 of the adjacent deck member 30 also secured to the beam. The openings 158 and holes 152 alternate in a longitudinal direction along the lap 136 of the other side 156. As seen in Figs. 6 and 7, the lap 136 of the other side 156 may include a slight fold 160 so that the lap 136 of the one side 150 and the lap 136 of the other side 156 may be positioned in overlying relationship and in parallel over the beam 26 or 28.

The standing seam flange 132 of each side 150 or 156 of deck member 30 presents its lip 134 which is oriented away from the standing seam flange 132 of the deck member 30 adjacent thereto. The respective standing seam flanges, shown as 132 and 132A in Figs. 6 and 7, present a space 162 therebetween which is preferably occupied by an insulation strip 164 which is preferably formed of synthetic resin foam material such as polyurethane in order to provide a thermal block and which maintains the juxtaposed flanges of adjacent deck members in spaced relationship. The lips 134 and 134A of the two standing seam flanges 132 and 132A are connected by batten closure 166 which extends longitudinally the length of the deck member 30 to provide weather resistance and some limited structural integrity for the roof formed by the adjacent deck members 30 and 30A. Batten closure 166 is partially open prior to installation and is hand crimped or mechanically crimped and seamed after installation.

The V-trusses 24 may be stored or transported in stack 98 as shown in Fig. 12. This is enabled by the ready detachability of reinforcing struts 58. Thus, prior to assembly, a number of the V-trusses can be stored in inverted, stacked relationship with their connecting plates 52 in superposed relationship. The reinforcing strut 58 shown at the bottommost V-truss 24 in stack 98 of Fig. 12 secures the stack 98.

To assemble the roof truss system 24, the V-truss 24 is turned or rolled upright at the job site with the bottom chord 34 positioned lowermost. Beams 26 (either 26A or 26B) and 28 are then fastened to the connecting plates 52 by temporarily using welded pins 94 and nuts 96 of the reinforcing struts 58 connected across the connecting plates 52. The deck member 30A is then placed in position over the V-truss system 22A as preassembled, or may be assembled at the job site by filling the area between upper membrane 124 and lower membrane 126 with polyurethane foam or some other insulation in insulation layer 128, fabrication of the panels not being within the scope of this invention but well understood by those skilled in the art. The deck member 30A can be connected to the beams in mechanically locking relationship by the use of screws 148. Preferably, one half (or every other one) of the screws 148 will be attached to hold the deck member 30A against its respective beam. This secures the deck members 30A in the first sequence for partial composite locking action. The deck members 30A are positioned with their riser 142 preferably against bight 112 and shoulder 144 resting on foot 116 or head 122. One or more additional deck members 30 can be placed on the deck member 30A and hoisted to the roof together with the V-truss system 22.

Once positioned on the roof, the top chords 26 and 28 are supported by masonry or girders as previously mentioned. V-truss systems 22 can be connected in end to end relationship to provide additional length to the span by welding, connecting plates or other methods well known in the art. The V-truss systems are also positioned in parallel to provide increased width to the roof structure, with adjacent V- truss systems 22 interconnected by connecting struts 32 as shown in Figs. 2 and 4. The deck members 30B may then be slid into position intermediate and in spanning relationship to the respective beams 28 and 26 of adjacent V-truss systems 22. Deck members 30B are positioned with their laps 136 over the laps 136 of deck members 30A so that the openings 158 are over heads 154 of screws 148 already fastened to the respective beams 26 and 28. Then another set of screws are inserted through holes 152 of the laps of both deck members 30B and 30A to penetrate leg 116 as shown by the cross mark in Fig. 9. This completes the final phase of the composite locking action for the roof system 20. With the deck members 30A and 30B securely fastened to the beams 26 and 28, insulation strips 164 are inserted in space 162 between each of the sides 150 and 156 presenting standing seam flanges 132 and covered by batten closure 166.

The resulting roof truss system 20 is designed to handle both vertical and horizontal forces as respectively indicated by the arrows 168 and 170 in Fig. 4. Load 168 includes dead loads such as the weight of the V-truss system 22 and the deck members 30A and 30B, as well as live loads and collateral loads as will be discussed hereinafter. It may be seen that an upward arrow is included in load 168, which can be caused by wind uplift forces imposed on the roof truss system 20. Load 170 is indicative of the compression forces induced by load 168 acting parallel to beams 26 and 28 serving as top chords and is taken by the deck member 30 including its upper membrane 124 and lower membrane 126, as well as beams 26 and 28.

The present design offers some significant advantages in handling these forces. First, the upper and lower membranes of the deck member 30 make available a cross sectional compression block area for resisting load 170. Second, the lever arm distance from the centroid of the bottom chord 34 (which will be in tension) to the combined centroid of beams 26 and 28 and the upper membrane 124 and the lower membrane 126 is substantially increased. These factors increase design efficiency and greatly limit the deflection of the V-truss systems 22.

Advantageously, the composite action roof truss system 20 hereof handles these forces 172 in the deck members 30B positioned intermediated the V-truss systems 22. The forces 172A and 172B include a diaphragm component of the lateral forces produced by wind or seismic activity which act on the building of which the invention hereof is a part. The lateral loads may thus be transferred to the whole system 20 to be carried as a whole by the diaphragm action across the beams 26 and 28 supporting the deck members 30B and to the next adjacent deck member 30A itself. The transfer of loads 170 and 172 and subsequent shear forces between the deck members 30 and the beams 26 and 28, and eventually along the stabilizer struts 46 is essential for composite design action of the entire structural assembly and may be computed by the formula:

V = MQ/I where: V=force to be developed by the fasteners

M= moment at theoretical cutoff Q= statical moment of area (roof panel) about the neutral axis of the combined section; and l=moment of inertia of combined section. Of course, the specific size of the rods and tubing, sheet metal, screw placement and component spacing will be dictated by the specifics of any design, given the span and load conditions. Typical truss spans along the length of each V-truss system may be up to 80 feet, with 50 to 60 feet being the most economical and in general will avoid the necessity to perform splicing of factory assembled deck members 30, although longer lengths are possible using intermediate splices. Widths of the deck members 30 may vary from 30 inches to 60 inches with 48 inches being an efficient width for most applications.

Any temperature stresses will become locked into the system as the deck members 30 are rigidly attached together. However, the entire system 20 will expand and contract with temperature, and any internal differential stresses become locked within the elements and will relieve only in the form of V-truss camber and minute deformations in the deck members 30 and the V-truss system 22. If the roof span were especially long, such as in excess of 400 feet in any direction, conventional expansion and contraction design elements would be included. In any event, redundancy and conservatism in compression elements of the design of the membrane system are required to guard against failure.

Claims

Claims:

1. A composite-action roof truss comprising: a plurality of elongated, spaced-apart beams; a V-truss extending substantially parallel to said beams for connecting to said beams; a deck member including upper and lower membranes and presenting opposed edges for mounting to said beams, each of said edges presenting an upstanding flange and a surface thereon for mounting said deck member to a respective one of said beams; and means directly fixing each of said surfaces to a respective one of said beams, said deck member acting as a top chord between said beams for transmitting both vertical and horizontal loads thereto.

2. A composite action roof truss as set forth in Claim 1 , said V-truss including a normally substantially horizontal reinforcing strut, said strut being positioned in vertically spaced relationship below said deck member.

3. A composite action roof truss as set forth in Claim 1 , said V-truss including a bottom chord, a plurality of V-struts extending substantially perpendicular thereto, and a plurality of stabilizer struts angled longitudinally relative to said V-struts.

4. A composite action roof truss as set forth in Claim 3, said V-truss including a plurality of plates for connecting one of said plurality of V-struts and one of said plurality of stabilizer struts to a respective one of said beams.

5. A composite action roof truss as set forth in Claim 4, wherein said plate is press formed to include a stiffener indentation therein.

6. A composite action roof truss as set forth in Claim 5, wherein each of said plates present recesses for receiving a portion of said V-strut and a portion of said stabilizer strut for placing the centroid of said V-strut and said stabilizer strut in alignment with said plate.

7. A composite action roof truss as set forth in Claim 1 , wherein said upper membrane and said lower membrane are juxtaposed to present at least one lap comprising said surface.

8. A composite action roof truss as set forth in Claim 7, wherein said lap of said lower membrane presents a shoulder for mating engagement with a corresponding complementary surface on said beam.

9. A composite action roof truss as set forth in Claim 1 , including insulative material positioned intermediate and adhesively bonding said upper membrane and said lower membrane.

10. A composite action roof truss as set forth in Claim 1 wherein said V-truss includes a bottom chord and at least one bottom chord secondary member connected to said bottom chord along at least a portion of the length thereof.

11. A composite-action roof truss system comprising: a plurality of elongated, spaced-apart pairs of beams; a plurality of deck members, each of said deck members including upper and lower membranes and presenting opposed edges for mounting to said beams, each of said edges presenting an upstanding flange and a surface for mounting each said deck member directly to a respective one of said beams; means fixing said surface of said edge directly to said beams with a first deck mer 3βr positioned in spanning relationship between each pair of beams and a second deck member positioned in spanning relationship between at least a first pair and a second pair of said beams, whereby the flanges of adjacent first and second deck members are juxtaposed; a plurality of V-truss members, one of said V-truss members positioned beneath each of said pair of beams; a reinforcing strut extending across each of said V-truss members for connecting respective beams in each pair; and a connecting strut extending between and connecting said first pair and said second pair of beams.

12. A composite action roof truss system as set forth in Claim 11, said V-truss members including a bottom chord, a plurality of spaced-apart V-struts oriented substantially perpendicular to said bottom chord, a plurality of spaced apart stabilizer struts angled longitudinally relative to said V-struts, and a plurality of connecting plates each connected to respective ones of said V-struts and respective ones of said stabilizer struts, and including means connecting at least one of said connecting plates to said connecting strut.

13. A composite action roof truss system as set forth in Claim 12, including means connecting at least one of said connecting plates to said reinforcing strut.

14. A composite action roof truss system as set forth in Claim 12, said connecting plate being press formed and including a stiff ener indentation therein.

15. A composite action roof truss system as set forth in Claim 12, said connecting plate being press formed and presenting recesses thereon for receiving a leg of said V-strut and an arm of said stabilizing strut whereby said leg and said arm are aligned with said plate.

16. A composite action roof truss system as set forth in Claim 11 , including a layer of insulation sandwiched between said upper and lower membranes.

17. A composite action roof truss system as set forth in Claim 11 , including a batten closure connecting said upstanding flanges of adjacent deck members to present a standing seam therebetween with said adjacent panels locked in composite action together and with a respective V-truss.

18. A composite action roof truss system as set forth in Claim 17, including an insulation strip positioned between the upstanding flanges of said adjacent deck members for providing a thermal block and maintaining said flanges in spaced relationship.

19. A roof truss system comprising: a pair of elongated beams; a V-truss for supporting said elongated beams in substantially parallel orientation, said V-truss including a bottom chord, a plurality of longitudinally spaced V-struts each presenting a pair of legs and an apex, said V-struts being connected to said bottom chord substantially at said apex, and a plurality of connecting plates respectively attached to each leg; means mounting said V-truss to said beams in force-transmitting relationship; a substantially planar deck member connected to said beams in spanning relationship to said beams, said deck member including an upper membrane, a lower membrane and an insulation layer sandwiched therebetween, said upper and lower membrane presenting a pair of laps respectively positioned for engagement with a corresponding one of said beams, each of said laps including a shoulder presenting a surface configured for engaging a corresponding beam to resist relative movement between said deck member and said corresponding beam in two transversely oriented planes.

20. A roof truss system as set forth in Claim 19, inc sing a mechanical fastener for securing each said lap to a respective beam.

21. A nestable roof truss comprising: a plurality of longitudinally spaced, generally parallel, substantially V- shaped primary struts each presenting an apex and a pair of divergent legs; a plurality of longitudinally spaced, generally parallel, substantially V- shaped stabilizer struts oriented in a transverse plane to said primary struts, each of said stabilizer struts presenting a pair of spaced-apart ends; a longitudinally extending bottom chord connected to the apices of said primary struts and said stabilizer struts whereby an apex of a primary strut is adjacent an apex of a corresponding stabilizer strut, said bottom chord defining a longitudinal axis; a plurality of connecting plates, each of said connecting plates being attached to both a leg of a primary strut and an end of a stabilizer strut; and a pair of stabilizer members connected to respective ones of said plurality of connecting plates, each of said stabilizer members extending substantially parallel to said longitudinal axis, whereby said truss presents a substantially V-shaped configuration along its longitudinal axis and is devoid of any obstruction extending transversely across said legs, thereby permitting nesting of said truss with other similarly configured trusses.